Vue.js is a lightweight front-end framework that adopts the MVVM architecture and aims to provide developers with a simple and efficient development method. The life cycle of Vue.js refers to a series of methods triggered during component creation, mounting, updating, and destruction. In this article, we'll take a deep dive into the Vue.js lifecycle.
Lifecycle of Vue.js components
The component life cycle of Vue.js can be divided into three phases: creation, update and destruction. In these three phases, Vue.js provides some hook functions, which can be triggered in different life cycles of components.
1. Creation phase
The component creation phase includes the creation of component instances, data initialization, template compilation and mounting, and other processes. At this stage, Vue.js provides the following hook functions:
- beforeCreate: It is called before the instance is created. At this time, the data and methods of the instance have not been initialized, and the data and methods cannot be accessed.
- created: Called after the instance is created. At this time, the instance has completed the data initialization, but the template compilation has not yet started.
- beforeMount: Called before the instance is mounted to the DOM. At this time, the template has been compiled, but the component has not been mounted to the page.
- mounted: Called after the instance is mounted to the DOM, and the component has been successfully rendered to the page.
In this stage, we can perform some data initialization operations, and also perform some DOM operations in the mounted hook function, such as requesting data, adding event listeners, and so on.
2. Update phase
The update phase of the component is triggered when the data changes. At this time, Vue.js will re-render the component to reflect the new data on the page. At this stage, Vue.js provides the following hook functions:
- beforeUpdate: Called before the data is updated. At this time, the data has been updated, but the component has not been re-rendered.
- updated: It is called after the data is updated. At this time, the component has been re-rendered, the DOM has been updated, and some DOM operations can be performed.
In this stage, we can perform some DOM operations in the updated hook function, such as updating elements in the page, recalculating the layout in the page, and so on.
3. Destruction phase
The component's destruction phase is triggered when the component is destroyed. At this time, the resources used in the component need to be cleaned up and released. At this stage, Vue.js provides the following hook functions:
In the component creation phase, Vue.js will first call the beforeCreate hook function, then call the created hook function, then call the beforeMount hook function, and finally call the mounted hook function to render the component on the page. In the update phase of the component, when the data changes, Vue.js will first call the beforeUpdate hook function, and then call the updated hook function to re-render the component. In the destruction phase of the component, Vue.js will first call the beforeDestroy hook function, and then call the destroyed hook function to release the resources used in the component.
It should be noted that during the life cycle of the component, different hook functions may be called multiple times, depending on the change of data and the way the component is used. Therefore, it is necessary to have a certain understanding of different hook functions in order to better understand the life cycle of components.
Application scenarios of Vue.js life cycle
The application scenarios of the Vue.js life cycle are very extensive. The following are some common application scenarios:
It should be noted that when using the Vue.js life cycle, it is necessary to select the appropriate hook function according to the specific application scenario to avoid unnecessary problems. At the same time, you need to pay attention to avoid too many operations in the hook function, so as not to affect the performance and user experience of the page.
Summarize
The life cycle of Vue.js is a very important concept. When developing Vue.js applications, we need to understand the life cycle of components in order to better grasp the use of Vue.js.
- beforeDestroy: Called before the component is destroyed. At this time, the component has not been destroyed, and some resource release operations can be performed.
- destroyed: Called after the component is destroyed. At this time, the component has been destroyed and all resources should be released.
In this stage, we can perform some resource release operations, such as unsubscribing events, unbinding, etc. It should be noted that if some asynchronous operations in the component are not completed, it may cause problems when the component is destroyed, so it needs to be dealt with in the beforeDestroy hook function.
Execution order of Vue.js life cycle
In the life cycle of components, Vue.js will trigger different hook functions in a certain order. The following is the execution sequence of the Vue.js life cycle:
- beforeCreate
- created
- beforeMount
- mounted
- beforeUpdate
- updated
- beforeDestroy
- destroyed
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In the created hook function, some data initialization operations can be performed, such as requesting data, calculating data, and so on.
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In the mounted hook function, some DOM operations can be performed, such as adding event listeners, updating elements in the page, and so on.
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In the beforeUpdate hook function, some data processing operations can be performed, such as filtering data, calculating data, and so on.
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In the updated hook function, some DOM operations can be performed, such as updating elements in the page, recalculating the layout in the page, and so on.
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In the beforeDestroy hook function, some resource release operations can be performed, such as unsubscribing events, unbinding, etc.
In the Vue.js life cycle, each hook function has its specific function, which can be used for data initialization, DOM operation, data processing, resource release and other operations. At the same time, the execution order of hook functions is also fixed, which can help us better understand the life cycle of components.
It should be noted that when using the Vue.js life cycle, it is necessary to select the appropriate hook function according to the specific application scenario, and avoid performing too many operations in the hook function, so as not to affect the performance of the page and user experience.
Finally, it should be emphasized that the life cycle of Vue.js is an abstract concept, and the specific implementation may vary with different versions or plugins. Therefore, when using the Vue.js life cycle, it is necessary to make corresponding adjustments and modifications in combination with specific versions and plug-ins.